1. Field of the Invention
This invention relates to the field of preparing 2-perfluoroalkylethyl alcohols through sulfation and hydrolysis of 2-perfluoroalkylethyl iodides and more specifically where an oxidant is part of the quench in the hydrolysis step.
2. Description of the Related Art
2-perfluoroalkylethyl alcohols (FA) are intermediates in the production of stain and oil resistant finishes for carpets and other such goods. Current processes for the production of 2-perfluoroalkylethyl alcohols incorporate a sulfation step and a hydrolysis step. In the sulfation step, 2-perfluoroalkylethyl iodides (PFAI) are reacted with sulfur trioxide. The fluorinated reactant is typically a perfluoroalkylethyl iodide mixture of the formula F(CF.sub.2).sub.2x CH.sub.2 CH.sub.2 I, wherein X is an integer from 1-10. The homologue distribution can vary, but a product mixture wherein X is predominantly 3, 4 and 5 is typically used. The sulfur trioxide is typically utilized as a 65% solution in concentrated sulfuric acid known as oleum, but not limited thereto. The sulfation reaction can be carried out with SO.sub.3 per se or with more or less concentrated oleum mixtures provided reaction stoichiometry requirements are satisfied. Specific reactant type/amount should be dictated by economic/process/safety considerations. In the hydrolysis step, the sulfation mass is drowned in water containing sodium sulfite to give 2-perfluoroalkylethyl alcohols.
During these reactions, various undesirable side products are formed, including 2-perfluoroalkylethyl iodides, the starting material. The 2-perfluoroalkylethyl iodides are not unused starting material, but instead are regenerated when iodide reacts with an unavoidable intermediate, such as perfluoroalkylethylsulfate or perfluoroalkylethyl bis sulfate.
This process is described in U.S. Pat. No. 3,283,012 by Day. This patent describes two reactions which are carried out in sequence. The first is the reaction of the iodide R.sub.f CH.sub.2 CH.sub.2 I with the oleum to form the fluoroalkyl hydrogen sulfate ester R.sub.f CH.sub.2 CH.sub.2 OSO.sub.2 OH and I.sub.2. The second reaction is the hydrolysis of the ester with aqueous acid to the alcohol, R.sub.f CH.sub.2 CH.sub.2 OH, and sulfuric acid.
Beck, in U.S. Pat. No. 4,618,731, teaches an improved process for the purification of 2-perfluoroalkylethanols in which unreacted iodides, having the formula R.sub.f CH.sub.2 CH.sub.2 I and R.sub.f I, are reacted with an excess of an alkali metal hydroxide and a C.sub.1 -C.sub.3 alcohol in a closed vessel at a temperature above 80.degree. C. until neither of said iodides can be detected in said 2-perfluoroalkylethanols.
The methods taught by Day and Beck contain somewhat undesirable options. Day's process does not use an oxidant in the hydrolysis step and, therefore, iodides are found in the product mixture. Because of this additional purification steps are be needed to obtain high purity product.
Beck's process is simply for purification of the alcohols. Use of this process, although it would give high purity alcohols, would result in longer processing times.
Beck, in U.S. application Ser. No. 07/530,351, filed May 30, 1990, discusses an improvement to Day's process using two similar continuous reactor systems combined in series, in each of which the reactants are contacted in zones of intense agitation in low-volume loops operated under pressure and at high rates of recycle. This method does not involve new chemicals and does not discuss the use of an oxidant in the hydrolysis step.
Foulletier et al., in U.S. Pat. No. 4,613,681, and Hoechst AG DE 3035641, describe the use of percarboxylic acids, both expensive and hazardous to use, for the conversion of the iodides to esters and alcohols. Also, this reaction is performed in an organic solvent.
Schwenk et al., in U.S. Pat. No. 4,219,681, describes the use of water in the presence of N-methyl-2-pyrrolidone for the conversion of 2-perfluoroalkylethyl iodides to alcohols. Yield of desired product is relatively low and distillation is required to recover the solvent and to separate the product alcohol from by product olefin.
Hayashi et al., in U.S. Pat. No. 4,001,309, report the use of water and various amides for the conversion of 2-perfluoroalkylethyl iodides to mixtures of 2-perfluoroalkylethyl alcohols and 2-perfluoroalkylethyl esters, the latter being converted to the alcohols by treatment with an alkali. The use of the relatively expensive organic amides and of high temperatures and pressures detract from this method.
In Allied Chemical Corp. DT 2628705, a process is described in which the iodides are treated with sulfur trioxide in sulfur dioxide. This method requires refrigeration and conversion is not complete.
Farbwerke Hoechst AG DT 2318677 discloses a hydrolysis at high temperatures and pressures resulting in a product or relatively low purity.
Atochem EP 245133A describes an electro chemical treatment of the iodide which also results in a relatively low purity alcohol.
Daikin Kogyo KK J55009025 discloses a process in which the iodide is sulfonated using chlorosulfonic acid. By-product gaseous hydrogen chloride must be collected and conversion of the iodide is relatively low.
Asahi Glass KK J50047912 reports the reaction of perfluoroalkyl iodides with water in the presence of acids and dimethyl formamide. Product purity is low.